1. Field of the Invention
The present invention relates to retractable panels and covering devices finding particular but not exclusive utility for covering various architectural openings such as windows, and as retractable space dividers. More specifically, the present invention relates to roller type mounting and deployment of light control window coverings having first and second parallel sheets and a plurality of transverse vanes connecting said sheets.
2. Description of the Prior Art
Fabric light control window coverings are known in the art, as shown in U.S. Pat. No. 3,384,519 to Froget. This patent discloses a window shade having two parallel mesh fabric sheets with a number of movable vanes disposed between the sheets. The parallel fabric sheets are movable relative to each other in order to control the angle of the vanes or blades. This shade is attached to a typical cylindrical roller shade head roller for rolling up the shade and controlling the angle of the blades. Similar disclosures are found in U.S. Pat. No. 2,029,675, U.S. Pat. No. 2,140,049, and French Pat. No. 1,309,194. German Pat. No. 382,758 discloses a similar window covering; however, instead of a cylindrical head roller, an elliptical head roller is provided.
As illustrated in the above disclosures, such a window covering is generally a sandwich of three layers which are attached together at various points. As the sandwich rolls around a roller, the layer around the outside must travel a greater distance than the inner layer, thereby compressing and wrinkling the layers. The thicker the sandwich is, and particularly the thicker the blades, the more pronounced this effect becomes. Thus, in practice with known deployment means, as the window covering rolls up around the head roller, the outer layer must stretch or the inner layer must buckle in order to accommodate the different distances that the two layers follow around the roller. Stretchy fabrics are undesirable because the blades would be unaligned in the lowered position and if non-stretchy fabrics are used the inner layer buckles. Such buckles can cause a permanent wrinkle or crease to develop in the fabric over time. This is because as the window covering is wrapped tightly around the roller there is a constant pressure compressing the buckle in the inner layer between the other layers and against the roller itself. In addition to an unattractive appearance, the buckles also create a high point on the roller which can occur unevenly and cause the window covering to roll up unevenly or skew to one side of the roller.
U.S. Pat. No. 4,344,474 to Berman discloses an insulated shade which includes a number of layers wrapped around a cylindrical head roller. While not a light control shade, the layers of the Berman shade appear to be connected together by bushings. Berman has recognized that the different layers will roll up at different rates and has provided journal plates having slotted holes to retain the bushings. This allows relative sliding between the bushings in an attempt to compensate for the different roll up rates of the different layers.
In roller shades in general it is important that the fabric be fastened to the head roller at an exact right angle to the cut edges of the fabric. This is to insure that the fabric rolls up straight along the head roller without skewing to the left or right. The curtain roller disclosed in U.S. Pat. No. 285,027 to Lobdell is an attempt to solve this problem in typical single sheet roller shades. Two slats are provided, one having tacks extending outward therefrom. The slot with tacks is positioned at the top of the curtain, at a right angle to the longitudinal line of direction of the curtain. The tacks are pressed through the curtain fabric and the second slat is pressed on to the tacks on the opposite side of the curtain. The slats attached to the curtain are slid into a complimentary groove in the roller. This construction has disadvantages in not being self aligning and requiring that the slats be placed very exactly on the curtain fabric.